Fullerenes are increasing becoming the focus of biochemical investigation as researchers continue to derivative the carbon cage to not only make it soluble in water but also make the fullerene cage biologically active in specific ways. These biochemical investigations of the fullerenes represent a new importance for the carbon cages in addition to the rapidly growing body of carbon cluster research. However, despite the widespread attention given to fullerenes, may fundamental questions remain either unanswered or in dispute. A prominent example is the thermodynamic stability of various cluster isomers at intermediate sizes. Accurately determining the relative stabilities of the cage, bowl, and ring isomers of C2O is a problem of long standing, and a definitive solution remains elusive. The answer lies in theoretical calculations performed with sufficiently accurate techniques in conjunction with large basis sets. In the proposed research, the C20 question will be answered through the use of the highly accurate coupled-cluster method (as CCSD(T)) and other sophistical methods in conjunction with the correlation-consistent basis sets developing by Dunning and co-workers. These calculations will be carried out on workstation computers with commercially available quantum chemistry upon chemistry software. Upon completion of the C20 project, the research will be expanded to include C24 and larger carbon clusters and may also include other cluster materials. The long- term goal is to observe trends in molecular stability over a range of sizes.